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The aim of this study was to find the effects of frozen storage on lipid and protein oxidation, firmness, liquid loss, sensory properties, and nutritional values in common carp (Cyprinus carpio) fillets during 6 months of frozen storage (–20 °C). Thiobarbituric acid‐reactive substances, peroxide value, and carbonyl concentration were significantly increased after the 4th, 2nd, and 8th weeks, respectively. The firmness of fillets decreased, whereas the liquid loss increased. In contrast, sensory evaluation did not show any significant changes. The amount of monoacylglycerols and diacylglycerols decreased significantly after 8 weeks. The L* and b* values increased significantly after the 16th and 3rd weeks but a* showed a minor increase. The value of pH increased significantly until the 4th week. The results indicate that the development of lipid and protein oxidation was not intense in the period of 24 weeks of frozen storage, and the fish was in an acceptable condition. Practical applications The demand of consumers for carp is increasing owing to the high content of essential polyunsaturated fatty acids. However, deterioration of fish fillets during the storage time can be a major problem as it leads to a loss of market acceptability. Therefore, monitoring the changes in lipids, proteins, sensory aspects, nutritional quality, and firmness during frozen storage is important. This study showed that after 24 weeks of storage at −20 °C, the products of lipid and protein oxidation increased but all the measured quality parameters were still within acceptable values.

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The aim of this study was to evaluate the main quality parameters in relation to two different carp culture systems. The quality of common carp fillet, such fat content, fatty acid composition, textural properties and sensory parameters, was evaluated. Carps were harvested from semi-intensive (SIS) and extensive (ES) systems, respectively. The results show no significant differences between the groups in organoleptic tests. However, significant differences (P < 0.05) were observed in the textual parameters (especially hardness). A difference in the fat content and fatty acid profile (P < 0.05) between two different carp culture systems was also observed. This study shows that the quality of common carp fillets particularly depends on the culture system used. Feeding strategies as well as general pond management are therefore of critical importance to enhance the overall quality of common carp fillets and meet the consumer demands. PRACTICAL APPLICATIONSThe present study gives insight into the effects of different rearing systems and feeding strategies on important quality properties such as fat content and texture of carp fillets. We showed that feeding strategies as well as general pond management are of critical importance to enhance the quality of common carp fillets and meet the consumer demands. Fish farmers can use the obtained knowledge to produce carp according to the customers demand. As consumer preferences with respect to fat content and softness have shown a regional variability, the used culture system and the resulting quality should be indicated at the market.

Proximate and fatty acid (FA) composition of seven freshwater fish species from the Czech Republic were examined. Moreover, the index of atherogenicity (IA) and the index of thrombogenicity (IT) were calculated from the obtained data. These two indices along with the total content of the essential n-3 FAs, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) as well as the ratio of n-6/n3 FAs, provide good indicators for the nutritional value of the fish. The species had been selected owing to the limited amount of information about their nutritional composition available. Furthermore, they are not typically subject to aquaculture, being almost exclusively obtained by angling. The protein content was relatively stable in all species (17.1 ± 1.55 to 19.2 ± 2.20 g/100 g). The content of carbohydrates ranged from 0.02 ± 0.1 to 0.99 ± 0.0 g/100 g and ash from 1.08 ± 0.20 to 2.54 ± 1.57 g/100 g. As expected, a high variability was observed in the fat content (0.74 ± 0.04 to 4.04 ± 0.81 g/100 g) and the FA composition, as well as the contents of EPA and DHA. IA and IT were close to the values stated for the Eskimo diet, indicating a high nutritional value with a positive effect for human health.

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This 4-month study (10 May -6 September 2012) evaluated the effects of supplementary feeding on common carp (Cyprinus carpio Linnaeus, 1758) growth, water quality, natural food availability and nutrient balance under different pond treatment regimes (eight rectangular earthen ponds; 0.03 ha surface area; 3-year-old carp). The nitrogen and phosphorus budgets were calculated as the difference between input (food, fish stocked and influent water) and output (effluent water and fish harvested). Three types of supplementary feeds were used: wheat, thermally-treated wheat, and thermally-treated and pressed wheat. An additional test group was provided with naturally available forage only and served as a control. The type of supplementary feed did not influence the water quality, with the exception of dissolved oxygen. No significant differences among experimental ponds were observed in zooplankton abundance. The use of modified cereals (especially thermally-treated and pressed wheat) improved carp growth performance and resulted in lower nutrient concentrations in effluent water via improving their digestibility. Both thermally-treated and thermally-treated and pressed cereals improved the balance of phosphorus; hence these diets could be beneficial, not only from the fish production point of view but also as a tool to reduce the deterioration of pond water quality.

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